Sentra
+ space (interior n boot)
+ averagely higher quality materials used than Vios (knock on d dashboard n door panels test)
+ ride on d firm side but still more comfortable than Vios
+ timing chain
- higher fc due to weight n mismatched engine to chasis, but acceptable for 1.6cc range
- vague steering

Vios
+ compact as in better parking n more suited for 4 adults max
+ better get-up-n-go due to power to weight ratio
+ better fc due to frugal engine n weight
+ better steering feedback than Sentra
- engine too noisy at highway speeds (similarly to Avanza, Rush which uses d same engine design n layout Xcept block material)
- less stable at 100kmh+ speeds n may sway at crosswinds in stock form
- lower material quality than Sentra (note that Vios was designed as a budget car to undercut Altis/Sentra category in d 1st place)
- rear head room (I'm 175 n still dun like d rear seats)
- timing belt

Others/Conclusion
Maintenence/Service availability n cost r generally almost d same n most mechanics should not hv any prob due to their simple designs n layouts.

Key deciding points:
Vios for fc n city driving
Sentra for comfort n long distance driving